The properties of pyriminyl (N-3-pyridylmethyl-N'-p-nitrophenyl urea) as a rodenticide against the lesser bandicoot rat (Bandicota bengalensis) in Rangoon, Burma, were investigated in the laboratory. The acute LD 50 and LD 95 dose of orally administered pyriminyl for B. bengalensis were found to be 6.7 mg/kg and 23.0 mg/kg of body weight respectively. When caged bandicoots were given a choice between plain and poisoned baits, the optimum rodenticidal concentration in the bait was found to be 0.25-0.5%. Symptoms of pyriminyl poisoning appear from 1 to 4 h after feeding starts, giving individual animals time to consume from 2 to over 30 LD 50 doses of 0.5% pyriminyl before feeding stops. Deaths occurred from 4 to 96 h after either oral dosing or free-choice feeding. There appeared to be no significant aversion to the poison at 0.25% or 0.5% concentration in foods. The potential hazards and use of pyriminyl as a field bait against populations of B. bengalensis are discussed.